I'd check the connections to the #4 plug and the #3 plug and make sure the ground on the end is good. You could also do away with the series plugs and put in the pencil style parallel plugs, put in a wires to each one, and remove the ground, and you'll have a parallel style system with pencil plugs. They make pencil plugs that fit. I did it to my 240 a while back and haven't looked back.

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